As the Chlamydomonas cell grows its basal bodies follow a cycle of duplication, movement and segregation which is closely coupled to the cell cycle. A genetic analysis of this basal body cycle is proposed, with the emphasis on the analysis of mutants in which segregation is aberrant. Because the Chlamydomonas basal bodies serve to nucleate flagella in interphase, such mutants have a distinctive vfl (variable flagella number) phenotype by which they can readily be recognized. Light and electron microscopy will be used to describe the mutants cellular phenotypes in detail. The structural basis of basal body segregation is of particular interest to us, and so special attention will be given to the connectors which link basal bodies to the nucleus and to one another. Their behavior will be followed throughout the basal body cycle, both in wild type and in vfl mutants. The Chlamydomonas basal body cycle is closely homologous to the centriole cycle as it exists in higher eucaryotes. In spite of much intense investigation, the centriole's cellular function remains mysterious. The proposed investigation provides a unique opportunity to explore the function of this organelle whose essence has eluded biologists for over a century.